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Powerful Tropical Cyclone Gita posed an increasing threat to Tonga on Sunday night. At 10:00 p.m. EST the center of Tropical Cyclone Gita was located at latitude 21.7°S and longitude 173.2°W which put it about 120 miles (195 km) east of Nuku’Alofa, Tonga. Gita was moving toward the west at 13 m.p.h. (21 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (205 km/h). The minimum surface pressure was 944 mb. Tropical Cyclone Gita was the equivalent of a major hurricane.

The circulation of Tropical Cyclone Gita is very well organized. There is a circular eye at the center of circulation. A ring of strong thunderstorms surrounds the eye and the strongest winds are occurring in that eye. Bands of showers and thunderstorms are revolving around the core of Tropical Cyclone Gita. Storms in the core are generating strong upper level divergence which is pumping mass away in all directions. Winds to hurricane/typhoon force extend out about 50 miles (80 km) from the center of circulation. Winds to tropical storm force extend out about 165 miles (270 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Gita is 23.6. The Hurricane Size Index (HSI) is 16.0 and the Hurricane Wind Intensity Size Index (HWISI) is 39.6. Those indices indicate that Gita will be capable of causing major damage when it moves over Tonga on Monday.

Tropical Cyclone Gita will be moving through an environment favorable for strong tropical cyclones during the next 24 to 48 hours. Gita will move over water where the Sea Surface Temperature is near 30°C. The upper level winds are weak and there is little vertical wind shear. The favorable environment could allow Tropical Cyclone Gita to intensify more before it reaches Tonga.

Tropical Cyclone Gita is moving north of a subtropical ridge which is steering the tropical cyclone toward the west. A general motion toward the west is expected to continue for another two or three days. On its anticipated track the center of Tropical Cyclone Gita could reach Tonga within 12 hours. Tropical Cyclone Gita will be capable of causing major wind damage when it reaches Tonga. Gita will also drop heavy rain and flooding is possible. Winds blowing the wind toward the coast could also produce significant storm surges in some locations.

Tropical Cyclone Gita strengthened on Saturday as it passed just to the east of Niue. Outer rainbands on the western side of Gita were bringing gusty winds and heavy rain to Niue. At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Gita was located at latitude 19.2°S and longitude 168.8°W which put it about 85 miles (135 km) east-southeast of Niue. Gita was moving toward the south at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (165 km/h). The minimum surface pressure was 969 mb. Tropical Cyclone Gita was the equivalent of a hurricane/typhoon.

The circulation of Tropical Cyclone Gita became more symmetrical on Saturday. Several rainbands wrapped completely around the center of circulation. A clear area appeared at the center of circulation on visible satellite images, which indicated that an eye was forming. A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in the ring. Storms in the core of the circulation were generating upper level divergence which was pumping mass away from the tropical cyclone. Other rainbands were revolving around the core of Tropical Cyclone Gita.

Tropical Cyclone Gita will move through an area favorable for intensification during the next 24 to 48 hours. Gita will move over water where the Sea Surface Temperature is near 30°C. Tropical Cyclone Gita is moving around the eastern end of an upper level low, but the upper level winds are weak and there is not much vertical wind shear. There is drier air to the southwest of Gita, but it does not seem to be entering the circulation of the tropical cyclone. Tropical Cyclone Gita will continue to intensify and it could strengthen rapidly. Gita could strengthen into the equivalent of a major hurricane.

The upper level low is steering Tropical Cyclone Gita toward the south. Gita will turn toward the southeast in about 12 to 24 hours. When Gita reaches the southern side of the upper low, it will move toward the west. On its anticipated track Tropical Cyclone Gita will pass just to the southeast of Niue. Gita could approach Tonga in about 36 hours and it could the equivalent of a major hurricane at that time.

Tropical Cyclone Gita formed near Samoa on Friday. At 10:00 a.m. EST on Friday the center of Tropical Cyclone Gita was located at latitude 14.8°N and longitude 172.3°E which put it about 155 miles (250 km) west of Pago Pago, Samoa. Gita was moving toward the east at 18 m.p.h. (29 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 989 mb.

Tropical Cyclone Gita was bringing gusty winds and heavy rain to Samoa. The strongest rainbands were north and east of the center of circulation. The bands south of the center consisted primarily of showers and low clouds. There appeared to be drier air in the southern half of the circulation which was inhibiting the development of taller clouds and stronger storms in that part of Gita. Thunderstorms in the rainbands north of the center of circulation were generating upper level divergence which was pumping mass away to the east of the tropical cyclone.

Tropical Cyclone Gita will be moving through an environment favorable for intensification. Gita will move over water where the Sea Surface Temperature is near 30°C. An upper level low south of Gita is producing easterly winds which are blowing toward the top of the circulation. Those winds are causing some vertical wind shear, but the shear does not appear to be strong enough to prevent intensification. The drier air in southern half of the circulation will inhibit intensification. However, if some of the rainbands north of the center wrap around the southern side of the center, then they could reduce the effects of the drier air. Tropical Cyclone Gita is likely to intensify into the equivalent of a hurricane/typhoon during the weekend.

The upper low south of Gita is currently steering the tropical cyclone toward the east. Gita will approach the eastern end of the upper low during the next 24 hours and it will move more toward the south. Tropical cyclone Gita will turn back toward the west when it moves south of the upper low. On its anticipated track Tropical Cyclone Gita will continue to bring gusty winds and heavy rain to Samoa for another 12 to 24 hours. Gita could pass near Niue in 24 to 48 hours and it could move near Tonga in about three days.

Tropical Cyclone Amos weakened as it sped past Samoa on Saturday. At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Amos was located at latitude 14.0°S and longitude 169.1°W which put it about 15 miles (25 km) north of Luma, Samoa. Amos was moving toward the southeast at 19 m.p.h. (31 km/h). The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h). The minimum surface pressure was 970 mb.

A ridge of high pressure east of Amos produced strong northwesterly winds which steered the tropical cyclone rapidly to the east-southeast on Saturday. Those steering winds carried the core of Amos just north of the larger islands of Samoa. Since hurricane force winds only extended out about 20 miles (30 km) from the center of circulation, the stronger winds stayed mostly over the open water. A weather station in Pago Pago, Samoa reported a wind gust of 54 m.p.h. (87 km/h).

Tropical Cyclone Amos is currently bringing wind and rain to the Manua Islands of eastern Samoa which include Olosega, Ofu and Ta’u. The rapid forward motion of Amos means that conditions should improve within a few hours.

The strong northwesterly winds are causing significant vertical wind shear that is rapidly weakening Tropical Cyclone Amos. Amos is still moving over water where the Sea Surface Temperature is near 30°C, but the vertical wind shear should continue to weaken the tropical cyclone as it moves farther east of Samoa.

Tropical Cyclone Amos intensified to the equivalent of a hurricane/typhoon on Thursday as it moved eastward across the South Pacific. At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Amos was located at latitude 12.4°S and longitude 177.1°W which put it about 80 miles (130 km) northwest of Iles Wallis. Amos was moving toward the east-northeast at 11 m.p.h. (18 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure 974 mb.

Tropical Cyclone Amos is a small, tightly organized storm. A primary band of thunderstorms wraps almost entirely around the center of circulation and an eyelike feature is visible intermittently on satellite imagery. Additional bands of showers and thunderstorms are spiraling around the core of the circulation. The thunderstorms are generating upper level divergence which is pumping out mass in all directions and causing the surface pressure to decrease.

The environment around Tropical Cyclone Amos is very favorable for further intensification. It is moving over water where the Sea Surface Temperature is near 30°C. The upper level winds are very weak and there is little vertical wind shear. Amos will continue to intensify on Friday and it could intensify rapidly.

A subtropical ridge north of Amos is steering the tropical cyclone toward the east and that general motion is expected to continue for several more days. On its anticipated track Amos will pass near Iles Wallis on Friday. Although the core of strongest winds will pass north of Iles Wallis, It could still bring strong winds, heavy rain and large waves to those islands. On its anticipated track Amos could be approaching western Samoa within 36 hours. It could be a very strong tropical cyclone at that time.

A center of circulation developed within a large area of thunderstorms north of Fiji on Wednesday and the system was designated as Tropical Cyclone Amos. At 5:00 p.m. EDT on Wednesday the center of Tropical Cyclone Amos was located at latitude 12.5°S and longitude 179.4°W which put it about 145 miles (235 km) northwest of Ile Futuna. Amos was stationary. The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 989 mb.

The circulation near the core of Tropical Cyclone Amos is still organizing. A narrow primary band of thunderstorms is wrapping tightly around the core and an eye may be forming at the center of circulation. Several other thin bands of showers and thunderstorms are rotating around the outer portions of the circulation. The thunderstorms are generating some upper level divergence, but it is not well developed yet.

The environment is favorable for continued intensification. Amos is moving over water where the Sea Surface Temperature is near 30°C. The upper level winds are not very strong and there is little vertical wind shear. As the core of the circulation becomes more well organized, it will convert energy from the ocean more efficiently and the wind speeds will increase. Tropical Cyclone Amos could intensify into the equivalent of a hurricane/typhoon within 24 to 36 hours.

Tropical Cyclone Amos is currently in an area where the steering currents are weak. An upper level ridge is forecast to develop north of Amos and begin to steer the tropical cyclone toward the east. On its anticipated track Amos could pass near Iles Wallis in 24 to 36 hours. It could be approaching Samoa in two or three days.

Strong upper level winds blew the upper portion of the circulation east of the surface circulation of Tropical Cyclone Zena as it passed south of Fiji. At 8:00 p.m. EDT on Wednesday the center of Tropical Cyclone Zena was located at latitude 21.5°S and longitude 176.0°W which put it about 60 miles (95 km) west of Nuku’ Alofa, Tonga. Zena was moving toward the east-southeast at 36 m.p.h. (58 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 988 mb.

Although Tropical Cyclone Zena briefly reached hurricane/typhoon intensity on Tuesday, it always consisted of a very small circulation which was very susceptible to vertical wind shear. When an upper level ridge northeast of Zena increased west-northwesterly winds over the top of the tropical cyclone, those winds blew the upper portion of the circulation east of the center. The circulation of Zena lost its vertical integrity and it was difficult to find a well defined center of circulation at the surface by late Wednesday. The remnants of Tropical Cyclone Zena are on a trend of rapid weakening. The vertical wind shear is expected to continue and Zena could dissipate within 24 to 36 hours while it passes south of Niue.

Strong Tropical Cyclone Winston passed over northern Tonga as it moved closer to Fiji on Thursday. At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Winston was located at latitude 17.6°N and longitude 175.1°W which puts it about 460 miles (740 km) east of Suva, Fiji. Winston was moving toward the west at 14 m.p.h. (23 km/h). The maximum sustained wind speed was 125 m.p.h. (205 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 941 mb. Tropical Cyclone Winston is the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale and it would be considered a major hurricane if it were over the Atlantic Ocean.

Winston is a small, compact tropical cyclone with a well organized inner core. It has an eye with a diameter of 15-20 miles (24-32 km) which is surrounded by a ring of strong thunderstorms. A couple of bands of convection spiral into the core, but Tropical Cyclone Winston possesses some of the characteristics of an annular hurricane.

Winston continues to move through a very favorable environment. The Sea Surface Temperature is near 30°C and upper level winds are relatively light. There is not much vertical wind shear. Tropical Cyclone Winston could intensify further on Friday.

A subtropical ridge to the south of Winston is steering the tropical cyclone toward the west-southwest. That general motion is expected to continue for another day or two. On its anticipated track Tropical Cyclone Winston could be very near the Lau Group of islands in eastern Fiji within 24 hours. Winston is expected to move across the Koro Sea and it could be near Suva within 48 hours.

Winston is a strong tropical cyclone and it could bring destructive winds and heavy rain to parts of eastern Fiji. It could also bring a storm surge and large waves, which may create dangerous conditions in low lying coastal areas.

Tropical Cyclone Winston intensified into the equivalent of a Major Hurricane on Wednesday before it made a slow turn back toward Tonga and Fiji. At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Winston was located at latitude 17.1°N and longitude 171.2°W which put it about 160 miles (255 km) north-northwest of Niue and about 240 miles (390 km) east-northeast of Neiafu, Tonga. Winston was moving toward the west at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 944 mb.

A very favorable environment of Sea Surface Temperatures near 30°C and little vertical wind shear allowed Tropical Cyclone Winston to intensify quickly into the equivalent of a Major Hurricane on Wednesday. Winston is a small, symmetrical tropical cyclone. There is a small, well formed eye at its center. The eye is surrounding by a ring of strong thunderstorms and there are several spiral bands rotating outside the eyewall. Hurricane force winds extend out about 40 miles (65 km) from the center and tropical storm force winds extend out about 140 miles (225 km) from the center.

Tropical Cyclone Winston could remain in a favorable environment for another 12 to 24 hours. It has the potential to intensify further during that time. After that time vertical wind shear could start to increase. Since the circulation of Winston is relatively small, fluctuations in intensity could occur more quickly.

A subtropical ridge south of Winston turned the tropical cyclone back toward the west on Wednesday. The ridge is expected to steer Winston slowly westward on Thursday. The subtropical ridge will steer it toward the west-southwest at a faster speed on Friday. On its anticipated track Tropical Cyclone Winston could approach the northern islands of Tonga in about 36 hours. It could be a very strong tropical cyclone at that time and Winston could bring strong winds and heavy rain to those islands. Winston could be approaching Fiji in about three days.

Tropical Cyclone Winston intensified rapidly on Tuesday as it moved east of Tonga. At 10:00 p.m. EST on Tuesday the center of Tropical Cyclone Winston was located at latitude 17.5°N and longitude 171.5°W which put it about 165 miles (270 km) northwest of Niue. Winston was moving toward the east at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h). The minimum surface pressure was 956 mb.

The upper level winds that were blowing over the top of Tropical Cyclone Winston diminished on Tuesday. The decrease in vertical wind shear allowed Winston to intensify rapidly and it is now the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale. Tropical Cyclone Winston remains in a favorable environment. It is over water where the Sea Surface Temperature is near 30°C. Winston has a well formed eye surrounded by an eyewall containing strong thunderstorms. Multiple spiral bands are rotating around the core of the circulation. Winston should continue to intensify and it could intensify rapidly on Wednesday.

A subtropical ridge to the northeast of Winston is slowing the eastward motion of the tropical cyclone. Winston could continue to move a little farther east on Wednesday before the ridge blocks its motion. The ridge is forecast to strengthen and extend to the west later this week. As the ridge extends westward it will force Winston to start to move back toward the southwest. On its anticipated track Tropical Cyclone Winston could move between Niue and Samoa on Wednesday. Winston could approach Tonga from the northeast as a much stronger tropical cyclone on Friday.